JP3475480B2 - Non-aqueous electrolyte secondary battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery and a method for producing the same, and more particularly to improvement of a positive electrode active material.

[0002]

2. Description of the Related Art In recent years, along with the breakthrough of various electronic devices, rechargeable secondary batteries have been researched as a power source that can be used conveniently and economically for a long time in response to the rapid progress.

Lead storage batteries, alkaline storage batteries, lithium secondary batteries (non-aqueous electrolyte secondary batteries) and the like are known as typical secondary batteries. Among them, the lithium secondary battery has advantages such as high output and high energy density.

This lithium secondary battery comprises a positive electrode capable of reversibly doping and dedoping lithium ions, a negative electrode, and a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent.

Generally, a solution prepared by dissolving a lithium salt in an aprotic organic solvent such as propylene carbonate is used as the electrolytic solution.

As the negative electrode active material, in addition to metallic lithium and lithium alloys, lithium storage materials capable of doping and dedoping lithium, such as conductive polymers, layered compounds such as carbon materials and metal oxides are used. To be

As the positive electrode active material, a metal oxide, a metal sulfide, a polymer or the like is used. In particular,
Non-lithium-containing compounds such as TiS ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ and lithium composite oxides already containing lithium have been proposed.

Among them, the lithium composite oxide has an advantage that it is produced from an inexpensive raw material, and particularly LiMn ₂ O ₄ having a spinel structure has the following excellent characteristics as a positive electrode active material. .

First, LiMn ₂ O ₄ exhibits a high potential of about 4 V against Li by extracting lithium. Therefore, a high energy density can be expected when it is used for the positive electrode of the lithium secondary battery [Journal of t
he Electrochemical societ
y, 137, 769 (1990)].

Here, when used in a potential range of about 4 V, the charging / discharging cycle of the battery starts from the charging process in which the negative electrode is doped with Li. Therefore, for example, even when a lithium storage material such as a carbonaceous material is used as the negative electrode active material, it is not necessary to store lithium in the negative electrode in advance before battery assembly, and the manufacturing process can be simplified accordingly.

Further, the carbonaceous material or the like used as the negative electrode active material usually has an irreversible lithium capacity which is not dedoped even when doped, which causes a loss of battery capacity. On the other hand, it has been reported that LiMn ₂ O ₄ can be doped with Li by an electrochemical method or a chemical method, whereby the Li composition ratio is 1 or more, that is, Li _{1 + x} Mn ₂ O ₄ (where x> 0 ). Therefore, if LiMn ₂ O ₄ is doped with Li in anticipation of the irreversible capacity of the carbonaceous material, the irreversible capacity is compensated, and a sufficient battery capacity can be obtained.

Further, LiMn ₂ O ₄ can have good reversibility by forming a solid solution with a metal element such as Fe or Cr, and can be repeatedly charged and discharged, which is often a problem in lithium secondary batteries. It is possible to suppress the accompanying decrease in capacity.

[0013]

However, the LiM
Although n ₂ O ₄ has many advantages as described above, for example, LiCoO, which is also used as a positive electrode active material, is used.
Compared to ₂ , the true density is low and the particle size is small. Therefore, when the electrode is configured, the bulk density of the electrode becomes small,
There is a drawback that the energy per volume cannot be raised sufficiently.

Further, although the raw material is inexpensive, the firing temperature is 700 because the grain size becomes fine when fired at a low temperature.
The temperature must be higher than ℃, and in some cases as high as 850 ℃, which is costly. For this reason, there is also a disadvantage that the low cost of raw materials does not lead to a sufficient reduction in production cost.

Therefore, the present invention has been proposed in view of such a conventional situation, and it is possible to obtain a high potential, have excellent reversibility, and compensate the Li content in accordance with the irreversible capacity of the negative electrode. It has a high bulk density, and realizes a positive electrode active material that can be produced at a low firing temperature by using an inexpensive raw material, and has high energy density and charge / discharge cycle characteristics and a highly productive non-aqueous electrolyte secondary battery, and It is an object to provide a manufacturing method thereof.

[0016]

The present invention is directed to LiMn ₂ O.
_By adding a small amount of a vanadium compound to the raw material composition of ₄ , and using the lithium manganese composite oxide obtained by firing this as a positive electrode active material, it is possible to improve the electrode bulk density and productivity of the positive electrode active material. To do. The point is to improve the filling amount of the active material per volume and to lower the firing temperature at the time of formation while maintaining the properties of LiMn ₂ O ₄ .

That is, in the non-aqueous electrolyte secondary battery of the present invention, the positive electrode active material is Li _x A _y Mn _2-y O ₄ (however, A
Is either Fe or Cr, and x is 0.9 ≦ x ≦ 2.
2, y is a mixed fired product of a lithium manganese composite oxide having a composition of 0 <y <0.4) and a vanadium compound, and the negative electrode active material is a carbonaceous material. .

In Li _x A _y Mn _2-y O ₄ , the initial Li composition ratio x is 0.9 ≦ x ≦ 2.2, and the Li composition ratio x during charging is x <0.5. It is characterized by being. Further, the present invention is characterized in that the vanadium compound is mixed in the positive electrode active material in a ratio such that the atomic ratio V / Mn of V and Mn is 0.001 to 0.05.

Furthermore, according to the method of manufacturing the non-aqueous electrolyte secondary battery of the present invention, Li _x A _y Mn _2-y O ₄ is used as the positive electrode active material.
(However, A is either Fe or Cr, and x is 0.9.
≦ x ≦ 2.2, y is 0 <y <0.4), and a mixed calcined product produced by heat-treating a mixture of a lithium manganese composite oxide having a composition of 0 <y <0.4 is used as a negative electrode active material. It is characterized by using a carbonaceous material.

In the non-aqueous electrolyte secondary battery of the present invention, as the positive electrode active material, lithium manganese in the form of Li _x n ₂ O ₄ or Li _x Mn ₂ O ₄ in which a part of Mn is replaced by Fe and Cr. composite oxide, i.e. _{Li x A y Mn 2-y} O
₄ (however, A is either Fe or Cr, and x is 0.
9 ≦ x ≦ 2.2, y is 0 <y <0.4), and a mixed fired product of a lithium manganese composite oxide represented by a composition formula and a vanadium compound is used. This is based on the following findings.

First, LiMn ₂ O ₄ is inexpensive as a raw material, can obtain a high potential as a positive electrode, and can be doped with Li by an electrochemical or chemical method, whereby the Li content can be increased. In addition to the advantages described above, there are many reports that characteristics are improved by solid-dissolving a different metal element.

For example, when LiMn ₂ O ₄ is produced, a compound such as Co, Cr, Fe or the like is mixed with the raw material composition at a rate of from several percent to 20 percent, and baked to obtain a single layer compound. It has been reported that the reversibility is improved. However, with regard to vanadium compounds, it is difficult to obtain a compound of a single layer even if it is added to the raw material composition of LiMn ₂ O ₄ , which leads to the improvement of characteristics as in the case of adding compounds such as Fe. It is said that there is no.

Then, the inventors of the present invention have made a detailed study in the case of adding the vanadium compound only in a small amount range, and found that the vanadium compound is LiMn ₂ O ₄
It was found that the particle size of the product becomes very large by adding it to the raw material composition.

That is, the vanadium compound is replaced with LiMn ₂
When an X-ray diffraction spectrum of a product obtained by firing a mixture of a small amount of O ₄ added to the raw material composition is observed,
A small peak is observed in addition to the peak at the same position as LiMn ₂ O ₄ . This means that a small amount of impurities are mixed in the product other than LiMn ₂ O ₄ , and the product is not a single-layer compound.

However, the mixture of impurities does not have a bad influence on the charge and discharge characteristics, and LiMn ₂ O ₄ produced by mixing the impurities has a larger particle diameter than that of LiMn ₂ O ₄ alone. This brings about a good result that the bulk density of the electrode can be increased.

Further, the vanadium compound is replaced with LiMn ₂ O ₄
When it is added to the raw material composition and fired, it acts so as to increase the particle size, so that the particle size does not become fine even if the firing temperature is set to a relatively low temperature. For this reason,
The firing temperature can be set lower than when firing only the raw material composition of LiMn ₂ O ₄ .

In the present invention, LiM is used as the positive electrode active material.
The reason why the mixed calcined product of n ₂ O ₄ and the vanadium compound was used was to aim at the effect of such a mixture of the vanadium compound.

That is, Li _x n ₂ O ₄ or Li _x Mn
A lithium manganese composite oxide in which a part of Mn of ₂ O ₄ is replaced with Fe and Cr, that is, Li _x A _y Mn
_{2-yO 4} (where A is either Fe or Cr,
x is 0.9 ≦ x ≦ 2.2 and y is 0 <y <0.4)
A mixed calcined product of the lithium manganese composite oxide and the vanadium compound represented by the following composition formula is calcined by mixing the vanadium compound while maintaining excellent characteristics of LiMn ₂ O _{4 as} a positive electrode active material. , Has a large particle size. Further, the particle size does not become fine even when the firing temperature is set relatively low. Therefore, by using this as a positive electrode active material to form a positive electrode, an electrode having a large bulk density can be obtained. As a result, the non-aqueous electrolyte secondary battery greatly contributes to improvement of energy per volume and reduction of production cost.

When Li _x Mn ₂ O _{4 in} which a part of Mn is replaced with Fe and Cr is used as the lithium manganese composite oxide, reversibility of the electrode is improved and charge / discharge characteristics are improved. To do. In this case, the composition ratio y of Fe and Cr is preferably less than 0.4.

The lithium-manganese composite oxide may be doped with Li in advance before assembling into a battery to compensate for Li corresponding to the irreversible capacity of the negative electrode. As a method of doping Li into the lithium manganese composite oxide, there are the following methods. (1) A method of electrochemically doping lithium-manganese composite oxide with lithium by performing discharge in an organic electrolyte by combining lithium-manganese composite oxide and lithium (2) Lithium-manganese composite oxide as a lithiation reagent (For example, n-butyllithium, naphthyl-lithium) to chemically dope the lithium composite oxide. Is.

Including pre-doping with Li,
It is desirable that the Li composition ratio x of the lithium manganese composite oxide be 0.9 ≦ x ≦ 2.2. However, this composition ratio range assumes the initial state before charging and discharging the battery. During charging when Li is dedoped from the positive electrode, the Li composition ratio x is 0. It is desirable to reduce it to less than 5.

On the other hand, the vanadium compound mixed in the lithium-manganese composite oxide may be any compound containing V, and oxides such as V ₂ O ₅ or hydroxides, nitrates, carbonates, sulfates and the like are used. be able to.

The amount of vanadium compound mixed is such that the atomic ratio V / Mn of V and Mn in the positive electrode active material is 0.001 to 0.001.
It is desirable to set the ratio to be 0.05. V /
When the Mn ratio is less than 0.001, the effect is insufficient, and when it exceeds 0.05, the vanadium compound may affect the charge / discharge capacity of the battery.

The mixed and burned material of the lithium-manganese composite oxide and the vanadium compound as described above is produced by mixing the raw material composition of the lithium-manganese composite oxide and the vanadium compound exemplified above and firing the mixture.

Here, the source of the lithium manganese composite oxide is
As the composition of the composition, LiMn₂O_FourTo generate
Mn₂O₃Manganese compounds such as LiOH, LiCO₃
A mixture of lithium compounds such as Also, Li
Mn₂O_FourLithium matrix in the form of solid solution of Fe and Cr
In the case of forming a gangan complex oxide, the above-mentioned LiMn ₂
O_FourFe in the raw material composition of₂O₃Fe compounds such as
Cr₂O₃A mixture of Cr compounds such as
It

In the present invention, the mixture of the lithium manganese composite oxide and the vanadium compound is used as the positive electrode active material as described above, but the negative electrode active material and the non-aqueous electrolyte that are usually used in lithium secondary batteries. Can be used.

As the negative electrode active material, lithium doping /
A carbonaceous material that can be dedoped is used. Besides, for example, a conductive polymer or a layered compound of a metal oxide may be used.

Further, as the electrolytic solution, LiPF ₆ , LiB
F ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃
Lithium salt such as ethylene carbonate, propylene carbonate, γ
-Butyrolactone alone or dissolved in a mixed solvent of diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, etc. is used.

[0039]

Function: Li _x A _y Mn _2-y O ₄ (where A is Fe,
Which is either Cr, x is 0.9 ≦ x ≦ 2.2, and y is 0 <y <0.4) and a mixture of a vanadium compound. Upon firing, the vanadium compound acts to increase the particle size of the product, and even when the firing temperature is set relatively low, lithium manganese composite oxide with a large particle size is produced in the form of mixed vanadium compounds. .

When an electrode is formed by using this product as a positive electrode active material, an electrode having a large bulk density and a high energy per volume is obtained because the positive electrode active material has a large particle size.

[0041]

EXAMPLES Preferred examples of the present invention will be described based on experimental results. In addition, Example 1-1, Comparative Example 1-1,
Comparative Example 1-2 and Example 1-2 are examples in which LiMn ₂ O ₄ is the main component of the positive electrode active material, and Example 2-1 and Comparative Example 2-1 are LiMn _1.8 Fe _0.2 O ₄ and Example. 3-1 and Comparative Example 3-1 are examples in which LiMn _1.8 Cr _0.2 O ₄ is the main component of the positive electrode active material.

Example 1-1 First, a positive electrode was prepared as follows.

Mn ₂ O ₃ , LiOH and V ₂ O ₅ were weighed in amounts such that the molar ratio was 1: 1: 0.02 and mixed well. Then, this mixture is heated in air at a temperature of 650.
Heated at ° C for 8 hours.

Observation of the X-ray diffraction spectrum of the obtained product revealed a small impurity peak in addition to the peak derived from spinel type LiMn ₂ O ₄ .

This product was used as a positive electrode active material, and graphite as a conductive agent and polytetrafluoroethylene as a binder were mixed in a weight ratio of 85: 10: 5, and 65 mg of this was mixed to obtain a nickel net current collector. Together with compression molding, a disk-shaped positive electrode having an outer diameter of 15.5 mm was produced.

The negative electrode material was obtained as follows. After cross-linking petroleum pitch until the oxygen content became 10%, the temperature was kept at 500 ° C. for 5 hours in an inert gas to obtain a carbide.
After crushing this, the temperature is set to 1200 ° C in an inert gas to
A negative electrode active material was obtained by heat treatment for a period of time. This negative electrode active material and polytetrafluoroethylene were mixed at a weight ratio of 9: 1, and 200 mg of the mixture was compression-molded together with a nickel net current collector into a disk shape having an outer diameter of 15.5 mm.
Then, this disk-shaped molded body was subjected to cathodic electrolysis in a nonaqueous electrolytic solution with Li as a counter electrode, and was doped with Li in an amount corresponding to 60 mAh to obtain a negative electrode.

The positive electrode prepared as described above, the negative electrode, the polypropylene porous film serving as the separator, and the mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 had a concentration of LiPF ₆ of 1 mol / l. A coin-type battery was assembled using the non-aqueous electrolyte solution dissolved in.

The charge-discharge characteristics of this battery were examined by repeating a charge-discharge cycle of charging it to 4.5 V with a constant current of 1 mA and then discharging it to 3 V. The result is shown in FIG. The discharge capacity is indicated by the capacity per 1 g of the positive electrode active material.

On the other hand, the product obtained by firing the mixture of Mn ₂ O ₃ , LiOH and V ₂ O ₅ as described above was mixed with polytetrafluoroethylene in a weight ratio of 95: 5.
Then, 1 g thereof was weighed and compression-molded to form a disk shape having an outer diameter of 15.5 mm and a surface area of 1.89 cm ² , and the thickness was measured. The bulk density obtained from this thickness based on the following equation was 3.28 g / cm ³ .

Bulk density = 1 / thickness (cm) × surface area (cm ² )

Comparative Example 1-1 A coin-type battery was prepared in the same manner as in Example 1-1, except that the product produced as described below was used as the positive electrode active material. The bulk density when mixed with the active material polytetrafluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, the atomic ratio of Mn ₂ O ₃ and LiOH is 1 :.
The amount was adjusted to 1 and mixed well. Then, this mixture was heated in air at a temperature of 650 ° C. for 8 hours.
The product thus obtained was used as the positive electrode active material.

The charge / discharge characteristics of the battery are shown in FIG. The bulk density of the positive electrode active material was 3.03 g / cm ³ .

Comparative Example 1-2 A coin type battery was prepared in the same manner as in Example 1 except that the product produced as described below was used as the positive electrode active material, and the charge / discharge characteristics were examined. The bulk density when mixed with the polytetrafluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, the atomic ratio of Mn ₂ O ₃ and LiOH is 1 :.
The amount was adjusted to 1 and mixed well. Then, this mixture was heated in air at a temperature of 850 ° C. for 8 hours.
The product thus obtained was used as the positive electrode active material. The charge / discharge characteristics of the battery are shown in FIG. The bulk density of the positive electrode active material was 3.15 g / cm ³ .

First, when the bulk densities of the positive electrode active materials obtained in Example 1-1 and Comparative Examples 1-1 and 1-2 were compared, vanadium was used as the raw material composition for producing the positive electrode active material. The bulk density of the positive electrode active material of Example 1-1 to which the compound was added was 3.28 g / cm ³ , and the positive electrode of Comparative Example 1-1, in which the vanadium compound was not used but the firing temperature was set to 650 ° C. The bulk density of the positive electrode active material of Comparative Example 1-2, which is significantly higher than the bulk density of the active material of 3.03 g / cm ³ and the firing temperature is set to 850 ° C. and higher, is 3.15.
It even exceeds g / cm ³ .

Also, looking at the charge / discharge characteristics shown in FIG. 1, the charge / discharge characteristics of the battery of Example 1-1 are those of Comparative Example 1 in which the vanadium compound is not used but the firing temperature of the positive electrode active material is set to be the same. -1 is better than that of the battery of Comparative Example 1-2 and is equivalent to that of the battery of Comparative Example 1-2 in which the firing temperature is set higher than that.

From the above, the addition of the vanadium compound to the raw material composition of LiMn ₂ O ₄ makes it possible to lower the firing temperature, increase the bulk density of the electrode, and improve the charge / discharge characteristics. It turns out to be effective above.

Example 1-2 In this example, the addition amount and the firing temperature when the vanadium compound was added to the raw material composition of LiMn ₂ O ₄ were examined.

A coin type battery was prepared in the same manner as in Example 1-1, except that the product produced as described below was used as the positive electrode active material, and the charge / discharge characteristics were examined. The bulk density when mixed with fluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, Mn ₂ O ₃ , LiOH and V ₂ O ₅ are
The Mn ₂ O ₃ and LiOH were weighed and mixed well so that the atomic ratio V / Mn to Mn with a molar ratio of 1: 1 and V was 0.001-0.05. Then, this mixture was heated in air at various temperatures for 8 hours. The product thus obtained was used as the positive electrode active material.

The bulk densities of the positive electrode active materials are shown in Table 1.
Table 2 shows the discharge capacity at the cycle.

[0063]

[Table 1]

[0064]

[Table 2]

First, as can be seen from Table 1, the bulk density of the positive electrode active material increases as the V / Mn ratio of the raw material composition increases at any firing temperature.

On the other hand, referring to Table 2, the discharge capacity is V / M.
Within a certain range of the n ratio, this range varies depending on the firing temperature, but increases as the V / Mn ratio increases, and when the n ratio exceeds the range, it decreases.

From this, it is understood that the addition amount of the vanadium compound added to the raw material composition has an optimum value.
That is, if the vanadium compound is added in an amount such that the V / Mn ratio is 0.001 to 0.05 as in this example, a sufficient discharge capacity can be obtained regardless of the firing temperature.

Example 2-1 A coin battery was prepared in the same manner as in Example 1-1 except that the product produced as described below was used as the positive electrode active material, and the charge / discharge characteristics were examined. The bulk density when mixed with the active material polytetrafluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, Mn ₂ O ₃ , Fe ₂ O ₃ , LiOH and V ₂ O ₅ were weighed in an amount such that the atomic ratio was 0.9: 0.1: 1: 0.02 and mixed well. Then, this mixture was heated in air at a temperature of 650 ° C. for 8 hours. The product thus obtained was used as the positive electrode active material.

The charge / discharge characteristics of the battery are shown in FIG. The bulk density of the positive electrode active material was 3.32 g / cm ³ .

Comparative Example 2-1 A coin type battery was prepared in the same manner as in Example 1-1, except that the product produced as described below was used as the positive electrode active material, and the charge and discharge characteristics were examined. The bulk density when mixed with the active material polytetrafluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, Mn ₂ O ₃ , Fe ₂ O ₃ and LiOH
Were weighed in an amount such that the atomic ratio was 0.9: 0.1: 1 and mixed well. Then, this mixture was heated in air at a temperature of 750 ° C. for 8 hours. The product thus obtained was used as the positive electrode active material.

The charge / discharge characteristics of the battery are shown in FIG. The bulk density of the positive electrode active material was 3.22 g / cm ³ .

Comparing the bulk densities of the positive electrode active materials obtained in Example 2-1 and Comparative Example 2-1, the vanadium compound was added to the raw material composition for producing the positive electrode active material. The positive electrode active material of No. 1 has a bulk density of 3.32 g / cm.
³ , the vanadium compound is not used, but the firing temperature is 7
The bulk density of the positive electrode active material of Comparative Example 2-1 set at 50 ° C. and higher was 3.22 g / cm ^{3 or} more.

Also, looking at the charge / discharge characteristics shown in FIG. 2, the charge / discharge characteristics of the battery of Example 2-1 were the same as those of Comparative Example 2-1 in which the firing temperature of the positive electrode active material was set higher than that. Is equivalent to.

From the above, even in a system in which Fe is solid-dissolved in LiMn ₂ O ₄ , adding a vanadium compound to the raw material composition makes it possible to lower the firing temperature and increase the bulk density of the electrode. It can be seen that this is effective in increasing the charge and discharge characteristics.

Example 3-1 A coin battery was prepared in the same manner as in Example 1-1, except that the product produced as described below was used as the positive electrode active material, and the charge / discharge characteristics were examined. The bulk density when mixed with the active material polytetrafluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, the _{Mn 2 O 3, Cr 2 O} 3, LiOH and V ₂ O _5, the molar ratio of 0.9: 0.1: 1 were weighed in an amount such that 0.02, and mixed well. Then, this mixture was heated in air at a temperature of 650 ° C. for 8 hours. The product thus obtained was used as the positive electrode active material.

The charge / discharge characteristics of the battery are shown in FIG. The bulk density of the positive electrode active material was 3.30 g / cm ³ .

Comparative Example 3-1 A coin-type battery was prepared in the same manner as in Example 1-1, except that the product produced as described below was used as the positive electrode active material, and the charge / discharge characteristics were examined. The bulk density when mixed with the active material polytetrafluoroethylene was determined.

The method for producing the positive electrode active material is as follows. That is, Mn ₂ O ₃ , Cr ₂ O ₃ and LiOH
Were weighed in an amount such that the atomic ratio was 0.9: 0.1: 1 and mixed well. Then, this mixture was heated in air at a temperature of 750 ° C. for 8 hours. The product thus obtained was used as the positive electrode active material.

The charge / discharge characteristics of the battery are shown in FIG. The bulk density of the positive electrode active material was 3.24 g / cm ³ .

Positive values obtained in Example 3-1 and Comparative Example 3-1
Comparing the bulk densities of the polar active materials,
Vanadium compound was added to the raw material composition at the time of generation
The bulk density of the positive electrode active material of Example 3-1 is 3.30 g / cm.
³And the firing temperature was set to 750 ° C and higher.
Bulk density of positive electrode active material of Comparative Example 3-1 3.24 g / cm 3. ³
Has exceeded.

Also, looking at the charge-discharge characteristics shown in FIG. 3, the charge-discharge characteristics of the battery of Example 3-1 were the same as those of Comparative Example 3-1 in which the firing temperature of the positive electrode active material was set higher than that. Is equivalent to.

From the above, addition of the vanadium compound to the raw material composition makes it possible to lower the firing temperature and to improve the bulk density of the electrode even in the system in which Cr is dissolved in LiMn ₂ O ₄ as a solid solution. It can be seen that this is effective in increasing the charge and discharge characteristics.

The present example is an example of a coin-type battery using a carbonaceous material that has been Li-doped in advance as the negative electrode, but the present invention is not limited to this, and the negative electrode is pre-doped with Li. Not using a carbonaceous material, the battery shape is not limited to the coin shape, and a cylindrical battery in which a positive and negative electrode active material is applied on a metal current collector and rolled up through a separator may be used. It may be a laminated type.

[0087]

As is clear from the above description, the present _{invention, Li x A y Mn 2-} y O as the positive electrode active material
₄ (however, A is either Fe or Cr, and x is 0.
9 ≦ x ≦ 2.2, y is 0 <y <0.4, and a lithium-manganese composite oxide and vanadium compound are mixed and fired, and a carbonaceous material is used as the negative electrode active material. The mixed calcined product has the characteristics that a high potential is obtained when it is used as a positive electrode, it has excellent reversibility, and that the Li content can be compensated in accordance with the irreversible capacity of the negative electrode, and the bulk density is high, and an inexpensive raw material is used. Can be used and produced at low firing temperatures. Therefore, it can greatly contribute to the improvement of the energy density and charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery and the reduction of the production cost.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing charge / discharge characteristics of a battery using LiMn ₂ O ₄ and V ₂ O ₅ as a positive electrode active material and a battery using only LiMn ₂ O ₄ as a positive electrode active material.

[2] only LiMn _1.8 Fe _0.2 O ₄ and V ₂ cells and LiMn a O ₅ and the positive electrode active material _{1. 8} Fe _0.2 O ₄ with characteristic diagram shown together charge and discharge characteristics of a battery that the cathode active material is there.

[3] only LiMn _1.8 Cr _0.2 O ₄ and V ₂ cells and LiMn a O ₅ and the positive electrode active material _{1. 8} Fe _0.2 O ₄ with characteristic diagram shown together charge and discharge characteristics of a battery that the cathode active material

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-84574 (JP, A) JP-A-4-233169 (JP, A) JP-A-6-140040 (JP, A) Naoaki Kumagai, etc. Synthesis of lithium-containing Mn02-V205 composite oxide from manganese (MnC03) and its electrochemical characteristics, Proc. , 3J03, P.I. 231 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/36-4/62 H01M 10/40

Claims (3)

(57) [Claims] 1. A positive electrode active material is _{Li x A y Mn 2-y} O 4
(However, A is either Fe or Cr, and x is 0.9.
≦ x ≦ 2.2, y is 0 <y <0.4), and is a mixed calcined product of a lithium manganese composite oxide and a vanadium compound, and vanadium is formed in the positive electrode active material.
And the atomic ratio V / Mn of V and Mn is 0.001 to 0.
The non-aqueous electrolyte secondary battery , wherein the negative electrode active material is a carbonaceous material, and is mixed in such a ratio as to be 05 . Wherein said _{Li x A y Mn 2-y} O 4 is the initial Li composition ratio x is 0.9 ≦ x ≦ 2.2, Li during charging
The non-aqueous electrolyte secondary battery according to claim 1, wherein the composition ratio x of x is <0.5. 3. A positive electrode active material comprising Li _x A _y Mn _2-y O ₄
(However, A is either Fe or Cr, and x is 0.9.
≦ x ≦ 2.2, y is 0 <y <0.4) and a vanadium compound are mixed.
And the vanadium compound is an atom of V and Mn
At a ratio such that the ratio V / Mn is 0.001 to 0.05.
A method for producing a non-aqueous electrolyte secondary battery, comprising using a mixed fired product produced by heat-treating a mixed mixture and using a carbonaceous material as a negative electrode active material.